In maintenance or repair of an automobile transmission, a vehicle hoist is used to raise the automobile from the ground and then a jack is used to support and raise or lower the transmission as necessary when removing or installing the vehicle's transmission. A conventional transmission jack as is known in the prior art is seen generally at 100 in FIG. 1. This conventional transmission jack has a base 102, a hydraulic cylinder 112, a pump 104 mounted to the base 102 which is operated by a pedal 106. Optionally, legs 108 and castors 110 can be attached to the base 102.
As is seen in FIG. 2, the hydraulic cylinder device 112 has an oil pressure cylinder 116 and a reservoir 118. The oil pressure cylinder 116 has a piston rod 114, to which a bracket is affixed at the upper end of the piston rod 114 to accept a transmission. The pump 104 is connected to the reservoir 118 by way of an oil withdrawing conduit 120 provided within the base 102. The oil pressure cylinder 116 is connected to the oil withdrawing conduit 120 by way of oil exit conduit 124.
Referring to FIG. 3, a check valve 136 is shown. An oil pressure release conduit 128 is provided above for connecting the oil exit route 124 and the reservoir 118. Pressure release valve 126 is installed for controlling the release volume. Further, an overload conduit 122, is used to connect reservoir 118 and the oil exit conduit 124 and is controlled by a safety valve 130.
In operation, an operator repeatedly steps on the pedal 106 of the pump 104, forcing the oil in the reservoir 118 to flow through the oil withdrawing conduit 120, through the oil exit conduit 124 and then into the oil pressure cylinder 116 of the oil cylinder 112 to raise the piston rod 114. In order to lower the piston rod 114 of oil cylinder 112 the oil release valve 126 is used to connect the oil release conduit 128 with the oil exit conduit 124 allowing the oil in the oil pressure cylinder 116 to return to the reservoir 118 so that the piston rod 114 is lowered to its original position. In the event that the load is beyond its rated load, oil delivered by stepping on the pedal 106 cannot be pumped out through the oil exit conduit 124, but pushes upon the check valve 132 in the overload conduit 122 and flows back to the reservoir 118 thus not allowing the operator to overload the jack and avoiding danger.
However, conventional transmission jacks as described above have been found to have problems in that the time taken to raise a single pump transmission jack through depressing the pedal was too long and the operator would fatigue and be unable to operate effectively. The transmission jack of the present invention remedies this problem by incorporating two pumps into a transmission jack which increases the amount of oil that is drawn out of the reservoir and pumped into the oil pressure cylinder to raise the piston rod and in turn the transmission at a faster rate.